Desensitization of solid organic peroxides



Patented Nov. 2, 1948 DEsENsITIzATmNoF SOLID ORGANIC PEROXIDES Harlow G.Hyatt, Buffalo, and Edward s. Shanley, Kenmore, N. Y,, assignors toBuffalo Electro-Chemical Company, Inc., Tonawanda, N. Y.

No Drawing.

The present invention detals with an improved 1 in sensitivity, providedthat the proper method of applying the desensitizer to the solid organicperoxide is employed.

It has been discovered, in accordance with the present invention, thatinert materials in general can be used for this purpose if they can beprecipitated from solution in finelydivided form upon the finelydividedsolid peroxide. In the preferred method of desensitizing, the solidperoxide, in a .veryfinely divided condition, is

stirred in an excess of water containing the desired desensitizer, or aconstituent thereof, in true solution. This slurryfiis then treated soas to cause precipitationof the inert desensitizing material fromsolution. This may be accomplished in any suitable fashion, for instanceby adding the remaining constituent of the desensitizer, by changing thepH, etc. At any rate, the materials must be so chosen, and the reactionso managed, that the solid phase, the organic peroxide,

remains virtually unchangedin appearance; presumably this indicates theprecipitation of the desensitizer upon the particles of peroxide in theslurry. The intimatelymixed solids may then be filtered off and dried inany conventional way.

The following examples are intended to illustrate the practice of thepresent invention? Example I .Desensz'tizing with calcium sulfate Twentygrams of finely divided benzoyl peroxide was suspended in 200 ml. ofwater containing 0.8 g. of calcium chloride. This slurry was treatedwith 100 ml. of an aqueous solution containing 1 g. of sulfuric acid.After stirring for a few minutes, the solds were filtered off and driedin a current of warm air. The peroxide, unchanged in appearance, wasfound to contain about 5% of calcium sulfate.

Impact sensitivity tests were made in 9. Bureau of Mines type impacttester. The peroxide of this Application January 27, 1945, Serial No.574,971

8Claims. (01. 260-510) example proved to have a probability of ignitionof 0.5 at kg. cm. impact.

A similar sample of dry, finely powdered ben zoy1 peroxide was tumbledin a ball mill for 2 hours with 5% of dry anhydrous, very finelypowdered calcium sulfate. This sample of peroxide, also diluted with 5%of calcium sulfate, was found to have a, probability of ignition of 1.0at 80 kg cm., which is the same as the figure for pure benzoyl peroxide.Thus, 5% calcium sulfate is found to reduce the probability of ignitionby when precipitated, and to have virtually no effect when mechanicallymixed.

Emample I I.-Desensitizin'g with Za m'c acid Twenty grams of powderedbenzoyl peroxide was slurried with 200 ml. of water containing 1.1 gramsof lauric acid. This solution was treated with a small amount of aceticacid, until the solution reacted acid to litmus. After stirring for ashort time, the solids were filtered off and dried. The dry peroxidemixture, which was found to contain 5% of fatty acids, was tested in theimpact machine. It proved to have a probability of ignition of 0.1 at120 kg. cm. Similar results are obtained by p'recipitatingfatty acidsfrom soap solutions by means of acid.

A similar sample of powdered benzoyl peroxide was tumbled in a ball millfor 2 hours with 10% of lauric acid, fine powder. The resulting mixturehad a probability of ignition of 0.6 at kg. cm. Thus, lauric acid at 10%concentration only slightly affects the sensitivity of benzoyl peroxide,when it is mixed mechanically, whereas 5% lauric acid, when precipitatedon the peroxide, results in a great reduction in sensitivity.

' Example IIL-Desensitizmg with aluminum hydroxide Twenty grams ofbenzoyl peroxide was suspended in 200 ml. of water containing 6.5 g.aluminum sulfate, hydrated. To this slurry ammonia was added until thepH reached 6, when the aluminum is quantitatively precipitated as thehydrate. The slurry was filtered and the solids were then dried in acurrent of warm air.

In an exactly parallel experiment, the same quantity of aluminum sulfatein the same quantity of water only, was precipitated with ammonia. Thisaluminum hydrate was filtered off and dried in a warm air current,parallel to the sample containing the benzoyl peroxide. This alumina,upon becoming dry, was powdered in a mortar and then mechanically mixedwith 20 g. of dry powdered benzoyl peroxide.

Impact tests on these samples showed a probability of ignition of 0.0 at100 kg. cm. for the peroxide carrying the precipitated alumina, whilethe peroxide mechanically mixed with the same quantity of alumina showeda sensitivity of 0.8 at 80 km. cm; virtually the same as undilutedbenzoyl peroxide.

Example IV.-Desensitz'zing with phthalic acid Twenty grams of benzoylperoxide was stirred into 200 ml. of water contaning 113' g. sodiumphthalate. To this solution was added dilute 4 which comprisessuspending the peroxide in a solution having a lauri-c acid compounddissolved therein and then precipitating lauric acid upon the peroxideand thereafter removing the so treated peroxide and drying the same.

4..Themethod' of reducing: the impact sensitivity of an organic peroxidewith phthalic acid which comprises suspending the peroxide in a solutionhaving a phthalic acid compound dissulfuric acid until the pH dropped toabout. 2.

The peroxide carrying the precipitated phthalic acid was filtered offand dried in warm air. The dried material proved to have a probabilityof ignition of 0.3 at 80 kg. cm.

A g. sample of powdered benzoyl peroxide was tumbled for two hours in aball mill with 2 g. of powdered phthalic acid. The resulting mechanicalmixture was found to have av prob.- ability of ignition of 0.7 at 80 kg.cm., when tested in-th'e Bureau of Mines type impact machine. Thus,mechanically mixed phthalic acidisshown to be. much less effective thanprecipitated phthalic acid, even when the former is used at twice theconcentration.

The foregoing examples are illustrative of :the invention vasxany of thesensitizers are operative provided the desensitizer is precipitated fromsolution in finely divided form upon the finely divided solid organicperoxide. Although the most widely employed methods of precipitationwill be by means .of .chemical reaction by double decomposition and bydecreasing the solubility of the desensitizer in a solvent, it will beunderstood that any means of precipitating the desensitizer is"comprehended within the scope of the invention.

What is claimed is:

1'. The method of reducing the impact sensitivity oia solid organicperoxide with calcium sulfate desensitizer which comprises suspendingthe peroxidein a solution of a soluble calcium salt and adding thereto-a;so1ublc sulfate=to-form "insoluble calcium sulfate which mingles withand coats the peroxide, the *aniountoi' desensitizer being Verysubstantially less than that requiredto effect a like desensitizingaction when 'm'ill'ed with the peroxide. I

2;The method of reducing the impact sensitivity of asolid organicperoxide with calcium sulfate .desensitizer which comprises suspendingthe peroxide in a solution of a soluble'calcium .sa'ltand adding theretoa-solublesulfate to form insoluble calcium sulfate which mingles withand :coats the peroxide and thereaftercollecting and drying thesolid-pthe-ramount of desensitizer being very substantially'less thanthat required to .eftect a like desensitizing actionwhen milled with theperoxide.

.3. Themethod of reducing the impact sensitivity :of. an organicperoxide withlauric acid ,solved therein and then precipitating phthalicacid upon the peroxide and thereafter removing the so treated peroxideand drying the same.

5'. The method. of reducing the impact sensitivi-ty of an organicperoxide with an insoluble organic acid which comprises suspending theperoxide in a solution containing a soluble salt of the organic aciddissolved therein and then precipitating the organic acid upon theperoxide and thereafter removing the so treated peroxide and drying thesame.

1 '6. The method of reducing the impact sensitivity-"of an organicperoxide with an insoluble organic acid which comprises suspending theperoxide in a solution containing a soluble salt of the .organic aciddissolvedv therein and then decreasing the pH of the solution untiltheorganic acidis precipitated upon :the peroxide and thereafterremoving. the. so treated peroxide and-drying the same.

7. The 'methodof reducing the impact sensitivity of a. solid organicperoxide which comprises precipitating from solution. upon the finelydivided peroxide a material 'known to desensitizewsolid organicperoxides when milled there- :withyand thereafter removing. the sotreated peroxide and drying th'e'same.

REFERENCES @ITEB The following references are file of this patent:

UNITED STATES PA EN S .Qi record :in the

